IF anyone still has any doubts that Mad Mel Gibson is off his rocker, you might want to check out his well-made but gratuitously violent “Apocalypto” – which makes “The Passion of the Christ” look like a church picnic.

Just make sure you haven’t eaten beforehand.

This 15th-century adventure (performed by a mostly nonprofessional cast entirely in subtitled Mayan) begins with natives eating genitals and depicts several beheadings as well as a heart being cut out of a living person’s chest in loving close-up.

Gibson has claimed in various interviews that the decline of Mayan civilization he depicts is an allegory for the ills of contemporary society, or some sort of commentary on the environment, the Bush administration, the war in Iraq or maybe his treatment at the hands of the LAPD.

Based on “Apocalypto,” that’s a pretty thin and unconvincing rationalization for a diseased mind who clearly gets off on depicting human suffering in the most graphic ways imagination, going back to “Braveheart.”

In “Apocalypto,” Native American Rudy Youngblood is Gibson’s Christ surrogate – he even takes a spear in his side – as an innocent young jungle dweller named Jaguar Paw.

The villagers’ idyllic existence is interrupted by the arrival of the fierce warrior Zero Wolf (Raoul Trujillo) and his heavily tattooed and pierced thugs from the big city, who lead away Jaguar Paw and the populace to be used for slavery and worse.

Jaguar Paw manages to hide away his pregnant wife (Dalia Hernandez) and their young son before he is taken to the great Mayan temple – where decapitated heads regularly roll down the bloody steps to applause from the masses – to be used as a human sacrifice.

Forget your history lessons about what an advanced civilization the Mayans were. Here they’re bloodthirsty savages, who seem to have even forgotten they invented astronomy when a cosmic occurrence spares Jaguar Paw’s life.

But he’s hardly out of the woods. The second – and more exciting – part of the movie is one very long chase (very reminiscent of “The Naked Prey”) as our hero tries to evade Zero Wolf and the sadistic Snake Ink (Rodolfo Palacios) en route to rescuing his family.

There is an especially amazing chase between Jaguar Paw and a jaguar – which climaxes with the jaguar chewing someone else’s face off. Gibson sure knows how to shoot a sequence, but he also doesn’t know when to stop with the blood, gore and maiming.

Eventually the violence is so utterly over-the-top that you can’t help but giggle. The subtitled dialogue doesn’t help, especially when people say things like “He’s f – – ked.”

There’s nothing overtly anti-Semitic here, and this isn’t a particularly pro-Christian movie, either, with the almost comical arrival of the Spanish conquistadors at the movie’s climax.

“Apocalypto” was financed out of Gibson’s pocket, reportedly for as much as $75 million. This nutso vanity project is being distributed by the Walt Disney Co., whose founder would be rolling in his cryogenic tube – if he hadn’t actually been cremated.

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APOCALYPTO

[**] (Two stars)

Bungle in the jungle.

In Mayan with English subtitles. Running time: 137 minutes. Rated R (graphic violence, gore, disturbing images). At the Empire, the Chelsea, the Village East, others.